diff --git a/docs/developer/code-style.md b/docs/developer/code-style.md
index 49ba7c52dd4a9e284905fb8d383384252b77c3a9..cf6e41731120551b9b5894a9920b199108c052f3 100644
--- a/docs/developer/code-style.md
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@@ -1,4 +1,6 @@
 # Developer - Code style
 
 - Variable names should alway be in *camelcase* and do **not** start with a capital letter
-- Class names should alway be in *Camelcase* and do **always** start with a capital letter
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+- Class names should alway be in *Camelcase* and do **always** start with a capital letter
+- Avoid using null, the Option type in scala can be used instead
+- If a method/value is designed to be overridden make it a `def` and override it with a `def`, do not use `val`
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